1. Field of the Invention
The present invention relates to a granular (or powdered) detergent composition containing an .alpha.-sulfo fatty acid ester salt. More specifically, it relates to a granular detergent composition having good granular or powder properties, without containing any phosphate, and having a less decomposable property of an .alpha.-sulfo fatty acid ester salt contained therein.
2. Description of the Prior Art
It is known in the art that various attempts have been made to develop a granular detergent composition having good granular or powder properties and good detergency, without using any phosphate, since the use of a phosphate in a detergent composition should be avoided from the view point of pollution. One attempt heretofore made was to use a new builder, typically an A-type zeolite. Another was to use, as an active detergent component, various surface active agents exhibiting good detergency even in water having a high hardness. Of these surface active agents, .delta.-sulfo fatty acid ester salts are to be noted since they have excellent detergency and soil dispersibility and also are not sensitive against calcium. Granular detergent compositions containing, as an active detergent component, these surface active agents are disclosed in British Patent Specification No. 1368736 and U.S. Pat. No. 3,915,881.
The granular detergent compositions containing the above-mentioned .alpha.-sulfo fatty acid ester salts have, however, the problem in that .alpha.-sulfo fatty acid ester salts are susceptible to hydrolysis during the production process or the storage thereof. The .alpha.-sulfo fatty acid ester salts are inherently likely to be hydrolyzed and be converted into .alpha.-sulfo fatty acid salts by cleavage of the ester linkage. The resultant .alpha.-sulfo fatty acid salts are only slightly soluble in water and have poor detergency.
In order to eliminate the above-mentioned problem, various attempts have been made to prevent the hydrolysis of .alpha.-sulfo fatty acid ester salts in the production of granular detergent compositions containing the same. For example, Japanese Patent Liad-Open Application (Kokai) No. 52-28507/1977 discloses that while the use of alkaline builder such as sodium silicate together with .alpha.-sulfo fatty acid ester salts remarkably decreases the detergency with the lapse of time due to the hydrolysis of .alpha.-sulfo fatty acid ester salts and while no use of an alkaline builder causes caking of the granular detergent composition, which remarkably decreases the commercial value of the detergent composition, use of a specific alkaline builder in a specific amount can prevent the decrease in detergency and prevent caking of the granules (or powder). Japanese Patent Laid-Open Application (Kokai) No. 52-117908 teaches the use of polyethylene glycol in a granular detergent composition containing .alpha.-sulfo fatty acid ester salts, in order to prevent hydrolysis of .alpha.-sulfo fatty acid ester salts during spray drying of detergent composition slurry containing .alpha.-sulfo fatty acid ester salts. Furthermore, Japanese Patent Laid-Open Application (Kokai) No. 50-151905/1975 discloses that (a) .alpha.-sulfo fatty acid ester salts in the form of granules or powder not only tend to form lower aldehydes or ketones due to the oxidative decomposition of the .alpha.-sulfo fatty acid ester salts themselves or their contaminants, i.e., unreacted fatty acid esters, but also tend to form fatty acid disalts due to the cleavage of the ester linkage and (b) the above-mentioned oxidative decomposition and cleavage of the ester linkage are further promoted when the granules of .alpha.-sulfo fatty acid ester salts are produced by means of spray drying. This publication proposes the use of hindered phenolic compounds and hydroxy polycarbonic acid salts to prevent the above-mentioned oxidative decomposition and cleavage of the ester linkage.